1. Field of the Invention
The present invention relates to a cassette containing at least one liquid crystal panel, and more particularly, to a cassette facilitating the inspection of at least one liquid crystal panel and a method of inspecting at least one liquid crystal panel.
2. Discussion of the Related Art
Generally, recent developments in technology have increased the demand for various types of display devices. In response to this increased demand, numerous types of flat panel displays (e.g., liquid crystal displays (LCDs), plasma display panels (PDPs), electro-luminescent displays (ELDs), vacuum fluorescent displays (VFDs), FED(field emission display), etc.) have been developed.
Owing to their large contrast ratio, low power consumption, and their ability to display gray levels and moving pictures, LCDs are ideal in for use in notebook personal computers, desk-top monitors, and televisions, and the like.
LCDs are fabricated using a series of fabricating processes including a substrate fabricating process, a liquid crystal panel fabricating process, and a module fabricating process.
The substrate fabricating process includes steps of forming an array of thin film transistors (TFTs) and pixel electrodes on a first substrate (i.e., a TFT substrate) and forming a black matrix, a color filter layer, etc., on a second substrate (i.e., a color filter substrate).
The liquid crystal panel fabricating process includes a step of bonding the TFT substrate and the color filter substrate together such that they are spaced apart at a uniform distance by a cell gap. The liquid crystal panel fabricating process further includes a step of injecting liquid crystal material into the cell gap.
The module fabricating process generally includes steps required to fabricate an operational LCD module after a signal processing circuit is fabricated.
A typical liquid crystal panel fabricating process will now be described in greater detail.
A first cassette (not shown), housing a first plurality of TFT substrates, and a second cassette (not shown), housing a second plurality of color filter substrates, are mounted into respective ports via loaders.
A plurality of gate lines are formed at fixed intervals along a first direction and a plurality of data lines are formed along a second direction, perpendicular to the first direction, on the TFT substrate. Accordingly, a plurality of pixel regions may be formed in a matrix pattern at the crossing of each of the gate and data lines. A plurality of pixel electrodes and a plurality of thin film transistors (TFTs) are formed at the pixel regions. A black matrix layer, color filters, and a common electrode are sequentially formed on the color filter substrate.
Next, each of the TFT and color filter substrates are unloaded from the first and second cassettes, respectively, using a robot arm programmed to select each of the TFT and color filter substrates one at a time.
Referring to FIG. 1, after an alignment material has been coated on the unloaded TFT and color filter substrates, an alignment process (1S) is performed on the coated alignment material to uniformly align liquid crystal material that is to be injected into the cell gap.
After the alignment process is completed, the TFT and color filter substrates are cleaned (2S), spacers are dispensed on the TFT substrate so as to ensure that the cell gap is uniform (3S), sealant is coated on an edge of the color filter substrate such that a liquid crystal injection inlet is formed (4S), and the TFT and color filter substrates are then bonded to each other (5S).
The bonded TFT and color filter substrates are then cut and processed into a liquid crystal panel (6S).
Subsequently, liquid crystal material is injected through the liquid crystal injection inlet into the cell gap of each of the liquid crystal panels and the liquid crystal injection inlet is then sealed (7S).
Lastly, the liquid crystal panel is inspected to determine the presence of any electrical failures and to evaluate the thermal stability of the injected liquid crystal material (8S).
The electrical failure inspection is performed by performing a lighting test on each of the liquid crystal panels using an A/P station. Inspection to evaluate the thermal stability of the injected liquid crystal material is performed by storing a plurality of liquid crystal panels in a substantially vertical position for a predetermined amount time at a constant, elevated temperature, (e.g., greater than room temperature).
A cassette, facilitating the transport and storage of a plurality liquid crystal panels, is therefore required in inspecting a plurality of the liquid crystal panels. The cassette is not only used in transporting, storing, and inspecting the plurality of liquid crystal panels, but is also used during the substrate, liquid crystal panel, and module fabricating processes.
FIG. 2 illustrates a perspective view of a cassette used in inspecting liquid crystal panels.
Referring to FIG. 2, a cassette used in inspecting liquid crystal panels includes a pair of side plates 17 having slots for supporting opposing edges of a plurality of liquid crystal panels 11, a frame 13 for supporting the side plates 17, and bars 15 for adjusting a distance between the side plates 17 in accordance with sizes of various the liquid crystal panels 11.
Slots 19 are arranged vertically along the side plates 17 for supporting the liquid crystal panels 11 arranged within the cassette. Dimensions of the slots 19 are maintained such that the area of the liquid crystal panels 11 contacting the slots 19 is minimized.
When the liquid crystal panels 11 are inserted into the cassette 30 as illustrated in FIG. 2, however, the productivity of an inspection of liquid crystal material for thermal stability and failure is minimized, as will be described in greater detail below.
FIG. 3 illustrates a diagram of a liquid crystal panel inspecting method and FIG. 4 illustrates a perspective view of a problem encountered during inspection when using cassettes such as those illustrated in FIG. 2.
Referring to FIG. 3, a plurality of liquid crystal panels 11 containing liquid crystal material that are to be inspected for thermal stability, are oriented substantially vertically within a cassette 30. The cassette 30 is then loaded into an oven 10 via a manually guided vehicle (MGV) 20.
After being heated for a predetermined amount of time, the cassette 30 is unloaded from the oven 10. Upon inspection, the thermal stability of the liquid crystal material within each of the liquid crystal panels 11 is evaluated. If it is determined that bubbles are present at an upper portion of the liquid crystal panels 11, the thermal stability of the liquid crystal material is determined to be insufficient and the liquid crystal panel is considered a failure. When the liquid crystal panels 11 are arranged within the cassette 30 in substantially vertical orientation, performing the thermal stability inspection may be facilitated as bubbles are generally easier to detect in liquid crystal panels oriented substantially vertically compared to liquid crystal panels oriented substantially horizontally.
The horizontal lengths of both the cassette 30 and the oven opening 10a illustrated in FIGS. 2 and 3, respectively, are greater than their respective vertical lengths. Accordingly, and referring to FIG. 4, liquid crystal panels 11 must be loaded vertically into cassettes such as those illustrated in FIG. 2 when the cassette 30 is loaded into the oven 10.
The liquid crystal panel arrangement illustrated in FIG. 4, however, is disadvantageous for the following reasons.
First, when the plurality of the liquid crystal panels 11 are inserted into the cassette 30 illustrated in FIG. 4, the liquid crystal panels 11 have a tendency to contact both side plates 17 and associated slots 19. Accordingly, the liquid crystal panels 11 provided in the arrangement described above may be scratched or broken when the cassette is loaded and unloaded into and out of the oven 10.
Second, when the plurality of liquid crystal panels 11 are inserted into the cassette 30, as illustrated in FIG. 4, they are generally inclined and thus remove space within the cassette 30 that would otherwise be available for other liquid crystal panels 11. Accordingly, space within the cassette is inefficiently managed.